Heretofore, images of high quality have been produced by thermal printers. In a typical thermal printer, an image is formed in three passes. First a dye donor having colorant such as yellow is placed in dye transfer relationship with a receiver and then the dye donor is heated in a pattern corresponding to the yellow portion of an image to be completed. Thereafter, cyan and magenta portions of the image are formed in a similar fashion. The completed color image on the receiver is continuous tone and in many cases can rival photographic quality.
In one type of thermal printer which prints color images, a donor contains a repeating series of spaced frames of different colorants such as heat transferable dyes. The donor is disposed between a receiver, such as coated paper, and a print head formed of, for example, a plurality of individual heating resistors. When a particular heating resistor is energized, it produces heat and causes dye from the donor to transfer to the receiver. The density or darkness of the printed color dye is a function of the energy delivered from the heating element to the donor.
Thermal dye transfer printers offer the advantage of true "continuous tone" dye density transfer. This result is obtained by varying the energy applied to each heating element, yielding a variable dye density image pixel in the receiver.
Thermal printers, as known in the computer printing art, have replaceable donor insertable thermal printer cartridges. These insertable thermal printer cartridges are capable of containing large volumes of donor necessary for printing many receivers which can be sheets of 81/2 by 11 inch coated paper. These insertable thermal printer cartridges, or their derivatives, are not suitable for inclusion in a digital camera as they are far too large. Additionally, the amount of donor per printed image is a variable depending upon the image to be printed and the size of the image to be printed with respect to the size of the receiver. Therefore, desktop printers teach the separation of the insertable thermal printer cartridges containing receivers from the insertable thermal printer cartridges containing donor material. In a digital camera, such a system has many inherent and undesirable limitations. First and most obvious is the complexity of having to load both a donor insertable thermal printer cartridge in one location and also a supply of receivers. Furthermore, cameras don't typically have interface and software means to input a user's change in receivers. Additionally, undesirable prints can be created by the wrong combination of donor and receiver placing an unnecessary burden on the user. An example of a portable thermal wax transfer printer not included within a digital camera that exhibits this problem is the Model GV-HT1 portable printer manufactured by JVC which requires a user to load an insertable donor cartridge as well as a separate supply of receivers.
Recently, ALPS Electric Co. has produced a very small thermal printer mechanism for integration into a digital camera. This printer, model PTML1101A has a mating insertable thermal printer cartridge that contains both donor in the form of a roll as well as small receivers positioned in the insertable thermal printer cartridge to receive dye from the donor by way of resistive heating elements in the printer. Resistive heating elements are very inefficient means for supplying the colorant sublimation energy and therefore place an unusually large burden on the power supply of the digital camera.